1. Field of the Invention
This invention relates to an in-line device for dampening pressure spikes and reducing “water hammer” caused by abrupt pressure changes within a pipe, hose, or flexible tubing when the flow of water (or other fluid flowing through the system) is shut-off.
2. Description of Related Art
Water hammer is a common occurrence when there is a sudden change in pressure in a pipe caused by shutting-off the flow of water through the pipe. Pressure spikes associated with quick shut-off valves can be 5 times or more greater than the normal pressure within the system. These changes in pressure may cause rattling and shaking of the pipes, producing the typical “hammering” noise associated with this problem, although the pressure change may cause damage to the piping system even when there is no hammering noise. The pressure spike can reverberate backward from a valve and cause damage to parts throughout the system, including fittings, valves, backflow preventers, and appliances connected to the piping system.
One way of preventing water hammer is by installing a water hammer arrester. These devices typically include a pipe, capped at one end, with a piston and a pressurized air pocket between the piston and the capped end, with the open end of the pipe connected to a pipe in the system just upstream of where a pressure spike may occur or connected at a valve and typically included in a valve outlet box. The arrester is typically installed perpendicular to the system pipe. When a pressure spike occurs, the pressurized water pushes against the piston in the arrester, which moves against the compressed air pocket until the pressure is stabilized and the piston returns to its normal, resting position within the arrester. This dampens the pressure so that it does not reverberate back through the piping system.
This type of prior art hammer arrester works well with fixed piping installations, but requires extra room for installation and larger sized outlet boxes to accommodate the arrester. Additionally, it is more difficult to install since it typically involves soldering pipe, compression joints, crimping on to PEX, or other various means of connections. If it becomes necessary to retro-fit a piping system with a hammer arrester, then the difficulty increases since it is more difficult to access piping within walls or to add a hammer arrester at an existing outlet box. This usually requires the assistance of a professional plumber and is not usually a do-it-yourself job for the average homeowner. Moreover, this type of design does not work with flexible hoses and tubing typically found on washing machines, dishwashers, and refrigerators/ice makers, even though the valves used with these appliances may cause severe pressure spikes.
In-line type arresters are also known, which have advantages over a T-connector style arrester, but these use dampening materials rather than pistons. For example, U.S. Pat. No. 6,672,337 discloses a cushioning diaphragm around a fluid chamber and U.S. Pat. No. 8,307,855 discloses a set of gas-filled balloons within a larger diameter pipe for dampening the pressure spike. A piston is more effective than cushioning materials.